Connecting ball joint, for example for an anti-roll bar of a running vehicle

ABSTRACT

The invention relates to a connecting ball joint ( 10 ), for example an anti-roll bar of a running vehicle, the ball joint ( 10 ) comprising a straight support ( 20 ) running along a general axis of elongation (xx′) and an elastically deformable member ( 30 ) mounted around the support ( 20 ). The ball joint has the characteristic that its elastically deformable member ( 30 ) comprises at least one laminated structure ( 35; 135 ) made up of (a) layer(s) ( 32 ) of elastically deformable flexible material and of (a) layer(s) ( 34 ) of more rigid material.

BACKGROUND

The invention relates to a connecting ball joint particularly for ananti-roll bar of a running vehicle, and especially for a bogie and/orbody of a high speed train.

In the particular, but nonlimiting, field of anti-roll bars (also knownas stabilizing bars or anti-sway bars) commonly used in automotive orrail suspension systems, the function of such a bar is to oppose thevertical forces transmitted to the wheels in bends when the inertia ofthe vehicle causes the latter to roll transversely.

The means of connecting or of fixing an anti-roll bar to the chassis ofthe vehicle or to the suspension arms may be varied and, in particular,may comprise bearings or ball joints provided, for example, with anelastic bushing. Such bearings or ball joints have various functions,aside that of fixing the bar to the chassis, such as the function offiltering the forces, during roll, between the structure of the vehicleand the bar, of the function of filtering low-amplitude vibration.

Various types of ball joint exist which allow a certain rotationaldeflection between two rigid parts. For example, the ball joint may befitted with a fairly thick rubber or polycarbonate bushing with africtional connection. It is also possible to anticipate the use oflubricated ball joints.

SUMMARY OF THE INVENTION

However, such ball joints are not yet satisfactory because they do notcorrectly filter vibration, and this leads to unpleasant noise due, forexample, to the excessive stiffness of the parts which prevent, orfollowing degradation of the parts which causes play and rattle. Theyare also not very strong. Finally, they do not have good ratios betweenangular excursion and stiffness (radial, rotational and conicaltorsional stiffnesses).

The object of the invention is therefore to solve at least some of theseproblems.

To do that, the invention relates to a connecting ball joint, forexample an anti-roll bar of a running vehicle, said ball jointcomprising a straight support running along a general axis of elongationand an elastically deformable member mounted around this support,characterized in that the elastically deformable member comprises atleast one laminated structure made up of (a) layer(s) of elasticallydeformable flexible material and of (a) layer(s) of more rigid material.

In general, the elastically deformable member will comprise means forpreloading its laminated structure, particularly for preventing theelastically deformable layer from working in tension.

According to one embodiment, the elastically deformable member maycomprise two coaxial annular laminated structures and two annular sleevetubes each mounted around one laminated structure to preload theirelastically deformable layers once these sleeve tubes have beenconnected together using fixing means, the ball joint then having aplane of section roughly perpendicular to the axis of the support.

In particular, the two sleeve tubes will each have a contact surfaceperpendicular to the axis of the support and will be welded peripherallyat these surfaces.

According to another embodiment, the elastically deformable member mayhave a plane of section passing through the axis of the support and maycomprise two approximately hemispherical laminated structures extendingalong the axis xx′ and two half sleeve tubes, also approximatelyhemispherical, each surrounding a laminated structure to preload theirelastically deformable layers.

In particular, an outer tube may be crimped around the half sleevetubes.

In order to allow good angular excursion of the ball joint, while at thesame time avoiding having to resort to a lubricant, each laminatedstructure will consist of an alternation of approximately hemisphericallayers of elastically deformable (hyperelastic) flexible material and ofapproximately hemispherical layers (or cups) of a more rigid material.The good shear properties of rubber are therefore put to full use inorder to improve this ability to rotate. Indeed this material has arelatively low shear modulus (of the order of 0.5 to 2 MPa) for a highcompression modulus (of the order of 1100 MPa).

Advantageously, each laminated structure will have a hyperelasticflexible layer at each of its ends, one in contact with a sphericalcore, and the other in contact with the preloading means.

By way of example, the hyperelastic flexible material may be a naturalrubber and the rigid material may be a metal, and the layers of flexiblematerial and the layers of rigid material may each have a thickness ofthe order of 1 mm.

In general, the ball joint also has a radial stiffness higher than theball joints of the prior art, for equivalent bulk and equivalentpossible excursion, and in particular have a radial stiffness which ishigher than its torsional and/or torsional conical stiffness.

In addition, the elastically deformable flexible layers are connected tothe more rigid layers in such a way that these flexible layers, whensubjected to rotational forces about the axis of the support or forcesof conical rotation about any axis perpendicular to the axis of thesupport, experience mainly shear forces, with no slipping with respectto the more rigid layers. Of course, these hyperelastic layers aresubjected to radial compressive (and tensile) stresses.

The invention also relates to an anti-roll bar for a running vehiclesuch as a high speed train, equipped with a connecting ball joint asdescribed hereinabove.

Other features, details and advantages of the invention will becomeapparent on reading the description which follows, given by way ofexample with reference to the appended drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of the ball joint according to the invention,

FIG. 2 is a side view of FIG. 1,

FIG. 3 is a sectional view of FIG. 1,

FIG. 4 is a detail view of FIG. 3,

FIG. 5 is an alternative form of embodiment of FIG. 3, and

FIG. 6 is a sectional view of FIG. 5.

DETAILED DESCRIPTION

FIG. 1 depicts a laminated ball joint 10, for example for anti-roll bar(not depicted) of a high speed train. This ball joint 10 comprises astraight support 20 extending along a main axis of elongation xx′ and anelastically deformable member 30 intended in particular to react theaxial and radial forces while at the same time allowing significantrotational deflection.

The elastically deformable member 30 comprises at least one laminatedstructure 35 surrounded by a preloading means 40. A detailed descriptionof this elastically deformable member 30 is given later on, inconjunction with FIGS. 3 and 4 in particular.

As can be seen in FIG. 2, the preloading means 40 and the laminatedstructure 35 are concentric, the laminated structure 35 being formed, aswill be seen later on, of a (approximately radial) stack of layers 32and 34 made of materials with different hardnesses.

FIGS. 3 and 4 show in greater detail the layers 32 and 34 of eachlaminated structure 35. As can be seen in particular in FIG. 3, theelastically deformable member 30 in fact comprises two laminatedstructures 35 which are annular and coaxial and which meet at a joiningplane perpendicular to the axis xx′ of the support 20. They need to bemounted on the support in such a way that their respective geometriccenters are roughly coincident. In practice, this center is locatedapproximately at the intersection of the axis xx′ and of the joiningplane of the two laminated structures 35, which, when the ball joint ispivoted (conical stressing) allows the layers to work in a shear.

The laminated structures are surrounded by sleeve tubes 42 and 44respectively, for example made of steel and acting, once fixed to oneanother, as a means for preloading (particularly for axially preloading)the laminated structures 35.

Each laminated structure 35 thus consists of an alternating stack oflayers 32 of an elastically deformable flexible material such as naturalrubber and of layers, or cups, 34, made of a more rigid material, suchas metal (building steel in particular).

An elastically deformable flexible material is to be understood asmeaning a material deemed to be hyperelastic, that is to say one whichhas the ability to be deformed elastically in at least one mostencouraged direction to a large extent, by contrast with a rigidmaterial which has a small zone of elastic deformation.

In addition, each laminated structure 35 begins and ends the stack witha layer 32 a/32 b of flexible material. Thus, one layer 32 a is incontact with one of the sleeve tubes 42 or 44, the other layer 32 b isin contact with a core 50 of spherical shape belonging to theelastically deformable member 30 and possibly also secured to thesupport 20. Adhesion between the rubber layers 32 and the metal parts(core 50, preloading means 40, cups 34) is achieved when the part ismolded by injecting rubber between the cups, through a chemicalreaction. This embodiment gives far better performance than bonding orany other means of connection.

Of course, each laminated structure 35 has an approximatelyhemispherical interior and exterior shape, which means that it perfectlyfollows the external shape of the spherical core 50 and the internalshape of the sleeve tubes 42 and 44.

As can be seen in detail in FIG. 4, the thickness of each layer isrelatively small, for example of the order of 1 mm in this instance. Thedimensions depend on the use to which this ball joint is to be put, andare therefore given only by way of indication. It is, however, importantthat the metal cups 34 have sufficient strength at the time of moldingthat they do not deform under the pressure of the rubber. Likewise, ifthe layers 32 of rubber are too thin, the material will have difficultyin flowing uniformly between the cups 34 during injection, and therewill then be a risk of creating empty pockets in the stack.

This ball joint 10 is particularly simple to produce and to assemble.

First of all, a first Laminated structure 35 is produced, trapping,during a first phase of injection-molding under pressure, rubber betweenthe various cups 34 and between a first cup 34 a and a half core 52, andbetween a last cup 34 b a sleeve tube 42. A unit assembly approximatelyin the shape of a ring or half ball joint is thus created. As the metalcups 34 have a hemispherical shape, as does the internal surface of thesleeve tube 42 and the external surface of the half core 52, the layers32/32 a/34 a of rubber also have a hemispherical shape.

The molding operation is repeated to form a second unit assembly (halfball joint) that complements the first, with a second sleeve tube 44, asecond laminated structure 35 and a second core 54.

These two half ball joints are then mounted around the support 20 so asto form the ball joint 10.

To do that, the two half cores 52 and 54 and the sleeve tubes 42 and 44and the laminated structures 35 are Drought axially closer together sothat the half cores touch to adopt a spherical shape. At that moment,the two sleeve tubes 42 and 44 are not yet in contact. The insidediameter of the core and the outside diameter of the support are chosenin such a way as to avoid any axial or torsional slipping of one halfcore with respect to the other when the ball joint is in use.

The sleeve tubes 42 and 44 are then forcibly brought closer together sothat they too come into contact with one another at contact surfaces 42a and 44 a which extend along a plane of section perpendicular to theaxis xx′ of the support 20. It is contrived that, when the half cores 52and 54 are butted against each other, the sleeve tubes cannot come intocontact with one another unless a certain axial force is exerted. Inother words, there is a certain axial clearance between the two sleevetubes before they are fixed together.

Next, the sleeve tubes 42 and 44 are held one against the other and areconnected, for example by a welding technique (preferably laser spotwelding) or by any other appropriate means which in particular is ableto react the axial forces generated by the preloading.

While the weld 48 is being formed, care is taken to prevent the rubberlayers 32 b from being damaged by the heat released. This is made easierin particular by spot welding and by a suitable design of the rubberlayers avoiding situating them too close to the welding zone.

Once the circumference of the sleeve tubes has been welded, it ispossible to anticipate carrying out an additional machining operation onthe part in order to remove any excess weld material.

It will be noted that both the sleeve tubes 42/44 and the rings 32/3 areidentical and arranged symmetrically on each side of a planeperpendicular to the axis xx′, so as to form a ball joint 10 which iswell balanced (give or take the manufacturing tolerances) about thisplane of section.

Bringing the sleeve tubes closer together along the axis xx′ of thesupport, and fixing the sleeve tubes together by welding so as to fillthe clearance left between them, have the effect of creating axialpreload in the laminated structures by shear and compression of therubber layers 32. This preload is particularly useful and in particularmakes it possible to limit the work that the rubber does in tension,which allows for a longer life.

All that then remains is for the ball joint 10 thus produced to be fixedto an anti-roll bar (or to a damping arm) or to a connecting link for abogie or body of a high speed train.

In general, this type of laminated ball joint has an elastic returnforce or moment in all directions, that is to say that applying a forcein one direction causes a more or less proportional displacement in thatdirection and that applying a conical torsion angle (about any axisperpendicular to the axis xx′) causes the appearance of a moment, thisalso being more or less proportional.

There is also a total absence of slippage of the elements one againstthe other, unlike in current ball joints, because the rubber layers infact experience shear in all possible directions of rotation.

The production of this laminated ball joint makes it possible to get asclose as possible to the model of the theoretical ball joint (threedegrees of freedom in rotation, no degrees of freedom in translation) byvirtue of higher stiffnesses in translation (axial and radial) and lowerstiffnesses in rotation (torsional and conical torsional) than withconventional (unlaminated) rubber-metal ball joints and thus make itpossible, for the same volume, to have higher forces and deflectionsthan in the prior art.

FIGS. 5 and 6 depict an alternative form of embodiment in which the balljoint 10 comprises two laminated structures 135 each consisting of astack of layers 32 of elastic material, such as natural rubber, and oflayers 34 of a more rigid material, such as a metal (conventionalsteel). These laminated structures 135 in the form of half shells with ajoining plane passing through the axis xx′ of the support 20, aresurrounded by half sleeve tubes 142 and 144 with the same plane ofsection, these half sleeve tubes acting as means 40 for preloading thelaminated structures 135.

Thus, in contrast with the previous embodiment, the half shells and thehalf sleeve tubes are therefore not annular and no longer meet on aplane perpendicular to the axis xx′ but on a plane passing through thisaxis xx′, as can be seen in FIG. 6. The half shells (and the two halfsleeve tubes) therefore extend along the axis xx′, each matching halfthe spherical shape of the core 50 support 20 over which the laminatedstructure is molded.

The way in which this elastically deformable member 30 is produced issimilar to that of the previous embodiment, except that the completeball joint is made in a single shot by molding the rubber between thecups 34, the half sleeve tubes 142 and 144 and the core 50. Preloading(mainly radial) is exerted at the time of this molding by the halfsleeve tubes 142 and 144 on the laminated structures.

An external tube 160 may also be crimped around the sleeve tubes to holdthe assembly in place and provide the preload, although this is notnecessary, it being possible for this preload to be provided byassembly.

The properties obtained with this type of ball joint are approximatelyequivalent to those of the first embodiment, except that the first balljoint has the same radial and conical stiffness regardless of thedirection in which the radial force or conical moment is applied.

It must of course however be understood that these examples are givenpurely by way of illustration of the subject of the invention, whichthey do not in any way restrict.

Thus, this type of ball joint may find a use outside the field ofanti-roll bars, for example in the field of attachments for dampers,draught arms, braking mechanisms, couplings, controls for pneumaticdevices or guide mechanisms. Nor is the ball joint according to theinvention restricted to use in the rail field; it may be applied to theaeronautical or automobile industry.

Furthermore, the spherical shape of the core 50 may be machined directlyon the support, without having to resort to an intermediate component.

Of course the number and thickness of the layers can vary according tothe required characteristics (radial, torsional and conical torsionalstiffness) and levels of deflection and load desired for these threetypes of stressing. The result, in terms of layer thicknesses mainly, isa compromise between the radial stiffness, on the one hand, and thetorsional and conical stiffness, on the other, and the forces and anglesto which the ball joint is subjected (maximum values and fatigue value).

The flexible layers may be made of natural rubber or of any othermaterial with hyperelasticity properties.

Finally, the welding of the sleeve tubes may be replaced by a fixingusing several screws which is arranged on lugs of each sleeve tube, bycrimping, or by any other equivalent means.

What is claimed is:
 1. Connecting ball joint (10), for an anti-roll barof a running vehicle, said ball joint (10) comprising a straight support(20) running along a general axis of elongation (xx′) and an elasticallydeformable member (30) mounted around the support (20), said elasticallydeformable member (30) comprising at least one laminated structure (35;135) made up of layers (32; 32 a; 32 b) of elastically deformableflexible material and of layers (34; 34 a; 34 b) of more rigid materialand means (40) for preloading said laminated structure (35:135),characterized in that the elastically deformable member (30) comprisestwo coaxial annular laminated structures (35) and two annular sleevetubes (42, 44) each mounted around one laminated structure (35) topreload their elastically deformable flexible layers (32; 32 a; 32 b)once said sleeve tubes (42, 44) have been connected together usingfixing means, the ball joint (10) having a plane of section roughlyperpendicular to the axis (xx′) of the support.
 2. Ball joint (10)according to claim 1, characterized in that the two sleeve tubes (42,44) each have a contact surface (42 a, 44 a) perpendicular to the axis(xx′) of the support (20), and are welded peripherally at the surfaces.3. Ball joint (10) according to claim 1, characterized in that eachlaminated structure (35; 135) consists of an alternation ofapproximately hemispherical layers (32; 32 a, 32 b) of hyperelasticflexible material and of approximately hemispherical layers (34; 34 a;34 b) of a more rigid material.
 4. Ball joint (10) according to claim 3,characterized in that each laminated structure (35) has a hyperelasticflexible layer (32 a) at each of its ends, one in contact with aspherical core (50), and the other in contact with the preloading means(40) of a more rigid material.
 5. Ball joint (10) according to claim 4,characterized in that the hyperelastic flexible material is a naturalrubber and the more rigid material is a metal.
 6. Ball joint (10)according to claim 4, characterized in that the layers (32; 32 a; 32 b)of elastically deformable flexible material and the layers (34; 34 a; 34b) of more rigid material each have a thickness of the order of 1 mm. 7.Ball joint (10) according to claim 1, characterized in that it has aradial stiffness which is high by comparison with either its torsionaltorsional conical stiffness.
 8. Ball joint (10) according to claim 1,characterized in that the elastically deformable flexible layers (32)are connected to the more rigid layers (34) in such a way that theflexible layers (32) experience, in operation, mainly shear forces, withno slipping with respect to the more rigid layers (34).
 9. Ball jointaccording to claim 1, characterized in that it has a radial stiffnesswhich is high by comparison with both its torsional and torsionalconical stiffness.